Merkittävä havainto tutkimustuloksista tehtiin kuparioksidin tunkeutumisesta vuoraustiileen kor-keakuparisissa näytteissä. Hehkutuksen johdosta kuparioksidi tunkeutui vuoraustiileen yhä syvemmälle ja yhä suurempina määrinä.The objective of the thesis was to study experimentally how a freeze-lining structure, which was formed on cold metal surface, changes or develops with over one hour of annealing at a temperature lower than normal process conditions on hot surface of copper flash smelting furnace. Duration of annealing and sample compositions were taken into consideration when the assessment of samples’ microstructure took place.

There were six samples to be annealed with different compositions. The copper concentrations of the samples varied between 21.5-38.0 wt%. From each of the samples, two pieces were cut for annealing. First of the pieces was annealed for 24 hours and the second for 192 hours. An annealing temperature of 900 °C was chosen. The actual annealing took place in a horizontal tube furnace with silicon carbide resistor in argon atmosphere (99.99 % Ar). The hot samples were let to cool down slowly in normal atmosphere after the annealing. Images were then taken from the annealed samples with SEM, and EDS analysis was performed for specific parts of the samples in order to find out the element composition. Lastly, the 24 hour, the 192 hour, and unannealed samples were compared together to see if there was any changes or development in the microstructure due to the annealing.

The most significant finding of the thesis was growth of delafossite in the samples due to annealing. Also, in the samples where delafossite needles were present, shrinkage of the needles were detected, as a consequence of the annealing. Because of the increase of the delafossite, the fraction of magnetite in the samples decreased. The annealing affected also the growth of the copper oxide. The increased quantity of the copper oxide manifested itself especially in more sizeable copper oxide grains in the glass matrix in the annealed samples.

A noteworthy observation was made in copper oxide penetration of refractory lining with the high copper concentration samples. Due to the extended annealing, the copper oxide penetrated the refractory lining more intensively and with larger quantities.